1. Field of the Invention
The present invention relates to a reel used in a preparation of a magnetic tape to wind a magnetic tape slitted in a narrow width. More particularly, it relates to a ribbed ring for winding a magnetic tape which has high bending strength and is not deformed during stacking of a plurality of the rings.
2. Description of the Prior Art
The ribbed rings for winding a magnetic tape are assembled with a spacer between adjacent rings and a winding shaft through which the rings and spacers are inserted so as to continuously wind magnetic tapes cut in each suitable width such as about 4 mm, at high revolutional velocity against winding resistance. Therefore, it is necessary to have sufficiently high strength so as to be durable under the severe conditions of high speed revolution and sudden stopping and high accuracy for winding under such severe condition, and to closely contact them without a gap when the ribbed rings are piled together for storage. In the stacked storage of the ribbed rings, it is necessary to fix the ribbed rings so as to prevent sliding and to prevent deformation thereof.
It has been known to fit each projection and each hole for mutually fixing reels for preventing sliding in the field of the reels for winding a magnetic tape. This structure has been used for ribbed rings. That is, several slits for fitting the ribbed rings to the winding shaft are formed at several positions on each inner surface of each ribbed ring and each projection for reinforcing each slit is formed around the slit and each concave or recess for receiving each projection for reinforcing is formed at the side of each reinforcing part. These parts have certain effect for stacking the ribbed rings however the parts have no effect for reinforcing the rings. Moreover, the reinforcing parts have no effect for reinforcing the rings themselves. When the reinforcing parts are provided, deformation of the rings made of a synthetic resin may be caused by the width deflection etc.